The invention concerns a profiled element for rotary drilling equipment, such as a drill stem or collar, interposed in a rotary drill pipe string.
In the field of prospecting and the exploitation of oil deposits, rotary drill pipe strings are used consisting of pipes and possibly other tubular elements connected end to end, according to the drilling requirements.
Such strings can in particular make it possible to produce deviating drillings, that is to say drillings where it is possible to vary the inclination with respect to the vertical or the direction in azimuth, during the drilling. In the case of greatly deviating drillings having practically horizontal portions, the friction torques due to the rotation of the drilling lining may attain very high values during the drilling. The friction torques may call into question the equipment used or the drilling objectives. In addition, it is often very difficult to bring up the cuttings produced by the drilling, because of the sedimentation of the debris produced in the drilling hole, in particular in the part of the drilling hole which is highly inclined with respect to the vertical. The result is poor cleaning of the hole and an increase both in the coefficients of friction of the pipes in the string inside the drilling hole and the contact surfaces between the pipes and the walls of the hole.
In order to reduce the coefficient of friction and the contact surface between the string and the walls of the drilling hole and to improve the cleaning of the drilling hole and the discharge of debris in the drilling fluid, there was proposed, in patent application FR-97 03207, a profile for a drill pipe which has a diameter greater than the diameter of the end portions coming into contact with the wall of the drilling hole and provides a certain degree of reduction in the friction between the drill pipe and the wall of the drilling hole. The end parts, which have hydraulic profiles, activate the circulation of the drilling fluid and detach the debris attached to the wall of the drilling hole and form turbulence areas.
In a more recent French patent application, FR-99 01391, a profiled element has been proposed for rotary drilling equipment making it possible to reduce the friction between the drilling equipment and a wall of the drilling hole at the abutment areas of the profiled element and to limit the risks of jamming of the drilling equipment, when the equipment is brought up inside the drilling hole.
To achieve this aim, there are provided, on the profiled element, hollow parts and radially projecting parts having an arrangement in a helix around the profiled element and having geometric and dimensional characteristics which vary according to the axial direction of the element. Preferably, the hollow parts or grooves in the profiled element disposed in helixes have a cross-section of transverse passage, in a plane perpendicular to the axis of the drilling equipment, which decreases in the axial direction and in the direction of circulation of a drilling fluid in a drilling annulus between the equipment and the drilling hole.
In this way, a circulation of drilling fluid is achieved in the circumferential direction around the abutment areas of the profiled element, which reduces the friction between the drill pipe and the wall of the drilling hole at the abutment areas.
The profiled element described in FR-99 01391 generally has, upstream of the abutment area, an area of activation of the circulation of drilling fluid in the annulus of the drilling hole or turbulence area, according to which the profiled element has helical grooves having a profile making it possible to clean the drilling hole and to drive the debris conveyed by the drilling fluid. In general terms, the grooves provided in the different areas of the profiled element are placed in line with each other, along the entire length of the profiled element. However, the drilling debris driven with the drilling fluid may have a tendency to collect at the profiled element, inside the grooves, and effective scavenging of the drilling hole is not always obtained because of an activated axial circulation essentially in contact with the profiled drilling element.
The aim of the invention is therefore to propose a profiled element for rotary drilling equipment for producing a drilling hole, having an overall shape of revolution and an axis directed along the rotation axis of the drilling and at least one area of abutment on the wall of the drilling hole extending in the axial direction of the profiled element and having a maximum diameter constituting the maximum diameter of the drilling equipment and a turbulence area for producing an activation of the circulation of a drilling fluid in the drilling hole around the drilling equipment, this profiled element making it possible to obtain a good circulation of the drilling fluid in the drilling hole, at the periphery of the drilling equipment, and effective scavenging of the wall of the drilling hole and an energetic entrainment of the drilling debris, in the direction of circulation of the drilling fluid.
For this purpose, the profiled element according to the invention has in addition a deflection area adjacent to the abutment area and to the turbulence area, extending in the axial direction of the profiled element having at least one surface inclined with respect to the axis of the drilling, whose meridian line, in an axial plane, moves away from the axis of the profiled element in the direction going from bottom to top, in the service position of the profiled element in the drilling hole.